Just started reading for the second time: Staying Fit Over Fifty, Conditioning for Outdoor Activities by Jim Sloan, pub by the Mountaineers, 2004.
Excellent book for elder athletes, outdoor enthusiasts who want to stay active or anyone wanting to maintain and improve fitness. While the title says after 50, it's really a good guide for anyone over 30. Sections cover exercise effects and aging; training effect; how much is enough; nutrition; effects of exercise on the brain. The second half focuses on specific activities .... Running, cycling, rowing, x-country skiing. swimming, hiking.....

Changed how I view aging and performing as an elder athlete. Full of the latest research and enjoyable to read. Check it out. Dave.